Manual bitmap frame capturer (#181)

@@ -62,7 +62,10 @@ internal constructor(
     }
 
     /**
-     * Creates a video track, recording video through the supplied [capturer]
+     * Creates a video track, recording video through the supplied [capturer].
+     *
+     * This method will call [VideoCapturer.initialize] and handle the lifecycle of
+     * [SurfaceTextureHelper].
      */
     fun createVideoTrack(
         name: String = "",

+import android.content.Context
+import android.graphics.Bitmap
+import android.graphics.Matrix
+import android.graphics.Paint
+import android.os.Build
+import android.view.Surface
+import org.webrtc.CapturerObserver
+import org.webrtc.SurfaceTextureHelper
+import org.webrtc.VideoCapturer
+
+/**
+ * A [VideoCapturer] that can be manually driven by passing in [Bitmap].
+ *
+ * Once [startCapture] is called, call [pushBitmap] to render images as video frames.
+ */
+open class BitmapFrameCapturer : VideoCapturer {
+    private var surfaceTextureHelper: SurfaceTextureHelper? = null
+    private var capturerObserver: CapturerObserver? = null
+    private var disposed = false
+
+    private var rotation = 0
+    private var width = 0
+    private var height = 0
+
+    private val stateLock = Any()
+
+    private var surface: Surface? = null
+
+    override fun initialize(
+        surfaceTextureHelper: SurfaceTextureHelper,
+        context: Context,
+        observer: CapturerObserver,
+    ) {
+        synchronized(stateLock) {
+            this.surfaceTextureHelper = surfaceTextureHelper
+            this.capturerObserver = observer
+            surface = Surface(surfaceTextureHelper.surfaceTexture)
+        }
+    }
+
+    private fun checkNotDisposed() {
+        check(!disposed) { "Capturer is disposed." }
+    }
+
+    override fun startCapture(width: Int, height: Int, framerate: Int) {
+        synchronized(stateLock) {
+            checkNotDisposed()
+            checkNotNull(surfaceTextureHelper) { "BitmapFrameCapturer must be initialized before calling startCapture." }
+            capturerObserver?.onCapturerStarted(true)
+            surfaceTextureHelper?.startListening { frame -> capturerObserver?.onFrameCaptured(frame) }
+        }
+    }
+
+    override fun stopCapture() {
+        synchronized(stateLock) {
+            surfaceTextureHelper?.stopListening()
+            capturerObserver?.onCapturerStopped()
+        }
+    }
+
+    override fun changeCaptureFormat(width: Int, height: Int, framerate: Int) {
+        // Do nothing.
+        // These attributes are driven by the bitmaps fed in.
+    }
+
+    override fun dispose() {
+        synchronized(stateLock) {
+            if (disposed) {
+                return
+            }
+
+            stopCapture()
+            surface?.release()
+            disposed = true
+        }
+    }
+
+    override fun isScreencast(): Boolean = false
+
+    fun pushBitmap(bitmap: Bitmap, rotationDegrees: Int) {
+        synchronized(stateLock) {
+            if (disposed) {
+                return
+            }
+
+            checkNotNull(surfaceTextureHelper)
+            checkNotNull(surface)
+            if (this.rotation != rotationDegrees) {
+                surfaceTextureHelper?.setFrameRotation(rotationDegrees)
+                this.rotation = rotationDegrees
+            }
+
+            if (this.width != bitmap.width || this.height != bitmap.height) {
+                surfaceTextureHelper?.setTextureSize(bitmap.width, bitmap.height)
+                this.width = bitmap.width
+                this.height = bitmap.height
+            }
+
+            surfaceTextureHelper?.handler?.post {
+                val canvas = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+                    surface?.lockHardwareCanvas()
+                } else {
+                    surface?.lockCanvas(null)
+                }
+
+                if (canvas != null) {
+                    canvas.drawBitmap(bitmap, Matrix(), Paint())
+                    surface?.unlockCanvasAndPost(canvas)
+                }
+            }
+        }
+    }
+}
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